Rotational position detecting apparatus

ABSTRACT

This invention discloses a rotational position detecting apparatus for an internal combustion engine for detecting the rotational position of a crank shaft of the engine. The apparatus comprises a rotating disk driven by the engine and giving a large number of angular information signals and also a rotating disk having one reference information on the periphery thereof, an angle sensor for detecting the angular informations on the disk, a rotational reference sensor for detecting the reference information on the disk, waveform reshaping circuits for reshaping the output signals of said both sensors, and an electric circuit for determining the angular position and the reference position from the outputs of said waveform reshaping circuits, wherein a logical product of the reshaped output of the angle sensor and the reshaped output of the reference sensor is implemented, and the time of either one of the rise or fall of an output signal of the logical product is set to be an angular position, while the other one is set to be a reference position.

BACKGROUND OF THE INVENTION

This invention relates to a rotational position detecting apparatus fordetecting the rotational position of the crank shaft of an internalcombustion engine, which can be applied to the ignition system of theengine.

Recently, in the ignition system of an internal combustion engine, ithas been proposed to calculate electronically the ignition time inaccordance with the operation state of the engine. If the ignition timeis set by a rotation angle of the crank shaft between its referenceangular position and an angular position for generating a spark afterthe rotational position of the crank shaft reached the reference angularposition, it is necessary to detect the rotational reference positionand the rotational angular position of the crank shaft. Conventionally,in order to meet this requirement, the angular position and thereference position have been detected as an angular signal and areference signal by independent or different sensors respectively.Therefore, in the conventional system the positional relation betweenthe angle and the reference signals varies with an error duringmanufacture, the number of revolution of the sensor, the temperaturecharacteristic and the threshold voltage of a waveform reshapingcircuit. Thus, it occurs that the reference signal and the angularsignal are generated within a very short time that an operationprocessing circuit yields an error signal of angle. There is a furtherproblem that it is difficult to obtain a constant phase between thereference signal and the angle signal.

In a further conventional method, a logical operation was implementedbetween the angle and the reference signals to determine the angularposition and the reference position from the result of the logicaloperation, however, the conventional methods are not sufficient toovercome the above drawbacks.

SUMMARY OF THE INVENTION

According to this invention, output signals of the angle sensor and therotational reference sensor are reshaped into rectangular waves and alogical operation between these waves is implemented. The angularposition is determined by any one of a rise or fall of the rectangularwave obtained by wave reshaping the output signal of the angle sensor,while the reference position is determined by another one of the fall orrise of the rectangular wave. It is an object of this invention toprovide a rotational position detecting apparatus for an internalcombustion engine free from any shift of reference signal, due to asetting error of a sensor and free from any operation error by keeping aconstant angular relation between the reference position and the angularposition, by using the above method of determining the angular andreference positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electric circuit diagram showing the first embodiment of anapparatus according to this invention.

FIG. 2 shows waveforms at some sections of the apparatus of FIG. 1 forthe explanation of the operation thereof.

FIG. 3 is an electric circuit diagram showing the second embodiment ofan apparatus according to this invention.

FIG. 4 is an elevational view showing schematically the mechanicalconstruction of a rotational detecting part of the apparatus of FIG. 3.

FIG. 5 is a diagram showing a magnetization state of a rotational bodyin the rotational detecting part of FIG. 4.

FIG. 6 shows waveforms at various parts of the apparatus of FIG. 3 forthe explanation of the operation thereof.

FIG. 7 is an electric circuit diagram showing the third embodiment of anapparatus according to this invention.

FIG. 8 shows waveforms at various parts of the apparatus of FIG. 7 forthe explanation of the operation thereof.

FIG. 9 is a perspective diagram showing schematically another embodimentof a rotational detecting part which may be applied to the apparatus ofFIG. 3 or to the apparatus of FIG. 7.

FIG. 10 shows waveforms at various parts of the apparatus of FIG. 3 whenthe rotational detecting part of FIG. 9 is applied thereto.

FIG. 11 shows waveforms at various parts of the apparatus of FIG. 7 whenthe rotational detecting part of FIG. 9 is applied thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be explained hereinafter with reference toembodiments shown in the drawings. In the first embodiment of FIG. 1,the reference numeral 1 denotes a disk for angle or, that is, a disk forobtaining an angular information, which disk rotates in synchronism withthe crank shaft of the internal combustion engine and on the peripheryof which many magnetic poles for angular information are magnetized inan equi-spaced fashion. 2 denotes a reference magnet, and 3 denotes adisk for reference or a disk for obtaining a reference information madeof non-magnetic material. The disk 3 rotates with the disk 1. Thereference magnet is buried in the reference position of the disk 3. 4denotes an angle sensor while 5 denotes a rotational reference sensor.These sensors 4 and 5 are constituted with magnetic resistive elements.6 and 8 denote reshaping circuits for the angle and the referencesignals respectively, which convert the output signals of the sensors 4and 5 into rectangular waveforms. 7 is a logic circuit, in which 71 is aNAND circuit, 72a and 72b and NAND circuits constituting an R-Sflip-flop circuit, 73 and 74 are resistors, and 75 and 76 arecondensers. The resistor 73 and the condenser 75, and the resistor 74and the condenser 76 constitute differentiation circuits respectively. 9is an output terminal for the reference signal. The reference positionis defined by a rise of the reference signal which appears at the outputterminal 9. 11 is an output terminal for the angular signal. The angularposition is defined by a rise of the angular signal which appears at theoutput terminal 11. The output terminals 9 and 11 are connected to anelectronic ignition time control means (not shown). Since various typesof electronic ignition time control means are publicly known, nodetailed explanation of it will be necessary. In FIG. 1, terminals witha symbol "+" are connected to a positive pole terminal of a constantvoltage power source.

Next, the operation of the above circuit construction will be explained.When the crank shaft of an internal combustion engine rotates, the anglesensor 4 generates an output waveform as shown in (b) of FIG. 2 everytime the crank shaft rotates for a certain angle. When the magnet at thereference position is opposed to the rotational reference sensor 5, thatis, when the crank shaft reaches the reference position, the rotationalreference sensor 5 generates an output waveform as shown in (a) of FIG.2. These waveforms are converted by waveform reshaping circuits 8 and 6for the reference and the angular signals respectively into rectangularpulses as shown in (c) and (d) of FIG. 2. The angular position isdefined by the fall of the pulse as shown in (d) of FIG. 2. In thiscase, since separate magnets and sensors are used for the reference andfor the angle respectively, it may occur that the phases of therectangular pulses generated by the waveform reshaping circuits 8 and 6shifts or changes with temperature or the number of revolutions, etc. asindicated by broken lines in (c) of FIG. 2. Therefore, if the rise ofthe pulse shown in (c) of FIG. 2 is used as the reference position, theangular position and the reference position may approach each other tosuch an extent that it causes an operation error in an operationprocessing circuit in the following state (not shown). It is preferable,therefore, that the reference positional signal be generatedsubstantially at the center of the period of the signal indicating anangular position.

In the embodiment of FIG. 1, therefore, a logical operation of thepulses shown in (c) and (d) of FIG. 2 is implemented by the NAND circuit71 to obtain an output as shown in (e) of FIG. 2. The R-S flip-flopcircuit is set and reset by the fall of this output and the fall of thepulse shown in (c) of FIG. 2 respectively through differentiationcircuits. Through this arrangement, the required reference position isobtained at the rise of the pulse of (e) in FIG. 2, as shown in (f) ofFIG. 2. This position is at the center of the angular position and doesnot change under the phase shift of the pulse shown in (c) of FIG. 2. Bythe use of the flip-flop circuit, the pulse of (f) in FIG. 2 appearsonly once at the reference position regardless of the number of falls ofthe pulse of (d) in FIG. 2, so that no error operation occurs.

FIGS. 3 to 5 show the second embodiment of this invention. FIG. 4 showsthe mechanical construction of the rotational position detecting part.10 denotes a disk for angle, on which many magnetic poles correspondingto angular informations are placed as shown in FIG. 5. 30 denotes a diskfor reference, on which many magnetic poles corresponding to angularinformation are placed in the same phases as those on the disk 10 butthe portion or magnetic poles corresponding to the referenceinformations are omitted as shown in FIG. 5. The both disks are fixed toa shaft 24 by a screw 23 through fixing disks 21 and 22. The shaft 24 isdriven by the crank shaft of the internal combustion engine. Around theperiphery of the disks 10 and 30, an angle sensor 40 and a rotationalreference sensor 50 are disposed to oppose the disk peripheriesrespectively. The sensors 40 and 50 arranged in the detecting head H atthe same position with respect to the axial direction to generatealternating current outputs of substantially the same phase as shown in(a) and (b) of FIG. 6.

FIG. 3 shows a circuit construction, comprising a waveform reshapingcircuit 60 for angle consisting of resistors 61 to 64, an adjustingresistor 65 and a comparator 66; a logic circuit 70 consisting of aninverter 701, a NAND circuit 702 and NAND circuits 703 and 704constituting a flip-flop circuit; a waveform reshaping circuit 80 forreference consisting of resistors 81 to 84, an adjusting resistor 85 anda comparator 86; a differentiation circuit 12 for angle consisting of acondenser 121, a resistor 122 and a diode 123; and a differentiationcircuit 13 for the reference consisting of a condenser 131, a resistor132 and a diode 133. 9a denotes an output terminal for the referencesignal while 11a an output terminal for the angular signal. The inputoperation level of the waveform reshaping circuit 60 for the angle isadjusted at L_(a) as shown in (a) of FIG. 6 by the adjusting resistor65. The waveform as shown in (a) of FIG. 6 of the angle sensor 40 isreshaped into a rectangular waveform as shown in (c) of FIG. 6. Theinput operation level of the waveform reshaping circuit 80 for thereference is adjusted at a value a little higher than the level L_(b)shown in (b) of FIG. 6 by the adjusting resistor 85. The waveform of therotational reference sensor 50 as shown in (b) of FIG. 6 is reshapedinto a waveform as shown in (d) of FIG. 6. Thus, the output waveform ofthe NAND circuit 702 becomes as shown in (e) of FIG. 6. The flip-flopcircuit of NAND circuits 703 and 704 is set by the fall of the outputsignal of the NAND circuit 702 and is reset by the fall of the outputsignal of the waveform reshaping circuit 80 for the reference. As aresult, the NAND circuit 704 generates an output as shown in (f) of FIG.6. The rise of the output signal of the waveform reshaping circuit 60for angle is differentiated by the differentiation circuit 12 for angleto generate a differentiated signal at the angular signal outputterminal 11a as shown in (g) of FIG. 6. The times at which thedifferentiated signals are generated are set or assumed as the angularpositions respectively. Further, the rise of the output signal of theNAND circuit 704 is differentiated by the differentiation circuit forreference 13 to generate a differentiated signal at the reference signaloutput terminal 9a as shown in (h) of FIG. 6. The time at which thedifferentiated signal appears is set or assumed as the referenceposition. In the circuit shown in FIG. 3, if a circuit which istriggered by the rise of the output signal is used as the circuit of thelatter stage, it is needless to say that the differentiation circuits 12and 13 may be omitted.

FIG. 7 shows an electric circuit diagram according to a third embodimentof this invention, in which a part of the circuit construction of FIG. 3is modified. In the circuit of FIG. 7, instead of connecting the outputterminal of the NAND circuit 704 to the differentiation circuit 13 forreference, the output of the NAND circuit 703 is connected thereto.Other parts of the circuit construction are the same as those of thecircuit of FIG. 3. Therefore, like reference numerals are used to denotelike parts as shown in FIG. 3. The outputs of the angle sensor 40 andthe rotational reference sensor 50 are applied to the circuit of FIG. 7in the same way as it is in the circuit of FIG. 3.

FIG. 8 shows waveforms of the signals at various parts of the circuit inFIG. 7. The waveforms shown in (a), (b), (c), (d), (e) and (g) of FIG. 8show the output waveforms of the angle sensor 40, reference sensor 50,waveform reshaping circuit 60 for angle, waveform reshaping circuit 80for reference, NAND circuit 702, and differentiated signal which appearsat the output terminal 11a of the angular signal respectively, which arethe same as the signals shown in (a), (b), (c), (d), (e), and (g) ofFIG. 6. As in the case of the circuit of FIG. 3, the input operationlevels of the waveform reshaping circuit for angle 60 and the waveformreshaping circuit for reference 80 are adjusted to be equal to the L_(a)level of (a) in FIG. 8 and a level a little more positive than the L_(b)level of (b) in FIG. 8, respectively. The waveform (f) in FIG. 8 showsthe output waveform of the NAND circuit 703 whose 1 and 0 signal levelsare opposite to those of the output waveform of the NAND circuit 704shown in (f) of FIG. 6. That is, at the rise and the fall of thewaveform (f) in FIG. 6, waveform (f) in FIG. 8 falls and risesrespectively. The waveform (h) in FIG. 8 shows the output waveform ofthe differentiation circuit for reference 13. The differentiationcircuit 13 differentiates the rise of the output signal of the NANDcircuit 703 to generate a differentiated signal as shown in (h) of FIG.8.

FIG. 9 shows the mechanical construction of a rotational detecting partused instead of the detecting part in FIG. 4. FIG. 10 shows thewaveforms of the signals at various parts of the circuit of FIG. 3. Whenthe rotational detecting part of FIG. 9 is used in place of thedetecting part as shown in FIG. 4. In FIG. 9, only the disk forreference 30 and the disk for angle 31 as shown in FIG. 4 are used. Tothe periphery of the disk 31 both sensors 40 and 50 are oppositelydisposed, which generate alternating current outputs as shown in (a) and(b) of FIG. 10. The outputs of these sensors 40 and 50 are reshaped orconverted into rectangular waveform signals as shown in (c) and (d) ofFIG. 10. The logical AND of these rectangular waveform signals areimplemented by an AND circuit (not shown) to generate a waveform asshown in (e) of FIG. 10, and the signal of (e) is applied to theinverter 701 and the differentiation circuit for angle 12 in FIG. 3instead of the output signal of the waveform reshaping circuit for angle60. As a result, the NAND circuits 702 and 704 generate outputs withtheir waveforms as shown in (f) and (g) of FIG. 10 respectively. Thedifferentiation circuits 12 and 13 produce outputs with waveforms asshown in (h) and (i) of FIG. 10.

FIG. 11 shows waveforms at various parts of the circuit in FIG. 7 in thecase when the rotational detecting part shown in FIG. 9 is used insteadof the part shown in FIG. 4. Waveforms shown in (a) to (f) and (h) ofFIG. 11 are the same as those shown in (a) to (f) and (h) of FIG. 10,respectively. The waveform shown in (g) of FIG. 11 is the outputwaveform of the NAND circuit 703 and the signal level of the waveform isa reverse of that of the waveform of (g) in FIG. 10 showing the outputof the NAND gate 704. Therefore, the waveform shown in (i) of FIG. 11which is the output waveform of the differentiation circuit 13 becomesdifferent from that of (i) in FIG. 10.

In the above-mentioned embodiments the sensors 4, 5, 40 and 50 areconstructed with a magnetic resistive element, however, they may beconstructed with a Hall element. Further, if the rotational body isconstructed with a disk of magnetic material toothed to have teethcorresponding to the angular information, the sensor may be constructedwith an electromagnetic pick-up made by combining a signal coil and apermanent magnet.

Although in the above-mentioned embodiments the time of the rise of therectangular pulse of the waveform reshaping circuits for angle 6 and 60is determined to be the angular position and the time of the fall of thepulse is determined to be the reference position, the angular and thereference positions may be determined by the fall and the rise of therectangular pulse respectively.

In the above-mentioned embodiments the output signal of the flip-flopcircuit is reset by the rear edge of the output signal corresponding tothe reference information of the waveform reshaping circuit for thereference, it may be reset by the fall or the rise of the output signalof the waveform reshaping circuit for angle which output signal appearsafter the rear edge of the output signal of the waveform reshapingcircuit for angle. In such a case, the reset point may be determined asthe reference position.

As described above, according to this invention, the angular andreference information of a rotational body is detected by the angle andthe reference sensors respectively, the output signals of both sensorsare converted into rectangular waves by waveform reshaping circuits forthe angle and the reference, a logical operation of the output signalsof the waveform reshaping circuits is implemented, either the rise orthe fall of the rectangular pulse of the waveform reshaping circuit forangle is determined as the angular position while the reference positionis determined by the fall or the rise. Therefore, between the referenceposition and the angular position a constant phase relation is kept andno operational error occurs. Moreover, the invention has an excellenteffect of avoiding any shift of the reference position due to a positionerror of the rotational reference sensor or variations in temperatureand number of revolutions.

We claim:
 1. A rotational position detecting apparatus for an internalcombustion engine having a rotatable output shaft comprising:disk meanscoupled to said rotatable output shaft, said disk means being providedthereon with a reference information and a plurality of equi-spacedangular informations; first sensor means positioned to face said diskmeans, said first sensor means providing a train of first output signalsin timed relation with the passing of said equi-spaced angularinformation therethrough; second sensor means positioned to face saiddisk means, said second sensor means providing a second output signal intimed relation with the passing of said reference informationtherethrough; first reshaper means connected to said first sensor meansfor reshaping said first output signals into a train of first pulsesignals; second reshaper means connected to said second sensor means forreshaping said second output signal into a second pulse signal; gatemeans connected to said first reshaper means and said second reshapermeans for gating said first pulse signals in response to said secondpulse signal; and bistable means connected to said second reshaper meansand said gate means, said bistable means being driven into a firststable state at the output change in said first pulse signals by rise orfall thereof, said first pulse signals being passed through said gatemeans, and being driven into a second stable state at the output changein said second pulse signals, wherein the time position where the outputof said bistable means changes to the first stable state defines areference position, and a time position at the fall or rise of saidfirst pulse signals, which fall or rise is opposite to the rise or fallof said first pulse signals to drive said bistable means, defines anangular position.
 2. A rotational position detecting apparatus for aninternal combustion engine having a rotatable output shaftcomprising:disk means coupled to said rotatable output shaft and havingtwo parallel circumferential tracks; first information means provided onone of said circumferential tracks of said disk means at everypredetermined angular interval; second information means provided on theother of said circumferential tracks of said disk means in phasedrelation with said first information means, said second informationmeans being omitted at a predetermined position; first sensor meanspositioned to face said one of said circumferential tracks for providinga train of first sensor signals in timed relation with the passing ofsaid first information means therethrough; second sensor meanspositioned to face said the other of said circumferential tracks forproviding a train of second sensor signals in timed relation with thepassing of said second information means therethrough; first reshapermeans for reshaping said first sensor signals into a train of firstpulse signals; second reshaper means for reshaping said second sensorsignals into a train of second pulse signals; gate means for gating saidfirst pulse signals in response to said second pulse signals; andbistable means driven into a first stable state at the output change insaid first pulse signals by rise or fall thereof, said first pulsesignals being passed through said gate means, and driven into a secondstable state at the output change in said second pulse signals whereinthe time position where the output of said bistable means changes to thefirst stable state being determined as a reference position, and a timeposition at the fall or rise of said first pulse signals, which fall orrise is opposite to the rise or fall of said first pulse signals todrive said bistable means, defines an angular position.